Bug 26150 – Negative values for animation-delay are ignored (treated as zero)

• Component: CSS
• Status: RESOLVED FIXED

[Haravikk]

According to the CSS Animation proposed specification (http://webkit.org/specs/CSSVisualEffects/CSSAnimation.html part 3.8), the animation-delay property, if set to a negative value, is supposed to start an element's animation immediately, but from an offset position within the animation.

For example, a value of -0.4s would create an animation that starts immediately, at 0.4 seconds until the end of the animation.

The provided URL demonstrates an intended use of this; notice that the segments of the "wheel" are pulsing in unison, however their starting-frames are supposed to be staggered so that the pulsing effect will move around the wheel, starting from "About" and then proceeding anti-clockwise to "Gallery" before starting again. This can be achieved by using equivalent positive delays, however 

It doesn't do to only half implement your own standards! =D

Otherwise great job though, the animation's are great.

[Mihai Parparita]

Created attachment 44350 [details]
Testcase

Simplified testcase. The second square has a -webkit-animation-delay of -1s, but its spin is synchronized with the first, implying a delay of 0.

[Shinichiro Hamaji]

Created attachment 44463 [details]
Patch v1

[WebKit Review Bot]

style-queue ran check-webkit-style on attachment 44463 [details] without any errors.

[Haravikk]

It's great to see progress on this, and to think the solution can be so small and elegant, thanks Mihai Parparita and Shinichiro Hamaji!

[Simon Fraser (smfr)]

Comment on attachment 44463 [details]
Patch v1

This patch works well for software-animated properties like 'left', but does not work for properties animated via GraphicsLayerCA, like -webkit-transform and opacity (you'll have to be on Mac OS X to test these).

[Shinichiro Hamaji]

Created attachment 44517 [details]
Patch v2

[Shinichiro Hamaji]

Thanks for the review! I added a similar fix for hardware animation
case and added a testcase where GraphicsLayerCA is used on Leopard.

Could you take a look again?

[Simon Fraser (smfr)]

Created attachment 44642 [details]
Revised patch

This patch is on top of the patch in bug 32387, which touches the same code.
It also adds a testcase for transitions with negative delay, which are affected by this change, and fixes the language in some comments.

[Shinichiro Hamaji]

Thanks for improving the patch! This looks great after you changed the semantics of setAnimationOnLayer.

[Simon Fraser (smfr)]

http://trac.webkit.org/changeset/52018